Endothelin receptor antagonists

ABSTRACT

This invention relates to novel endothelin receptor antagonists, derivatives, acceptable acid addition salts, solvates, hydrates and polymorphs thereof. The invention also provides compositions comprising a compound of this invention and the use of such compositions in methods of treating diseases and conditions that are beneficially treated by compounds that block the endothelin signaling pathway that leads to vasoconstriction and in particular those diseases or conditions beneficially treated by endothelin receptor antagonists.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/884,654, filed on Jan. 12, 2007. The entire teachings of the aboveapplication is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to novel endothelin receptor antagonists,derivatives, and pharmaceutically acceptable acid addition saltsthereof. The invention also provides compositions comprising a compoundof this invention and the use of such compositions in methods oftreating diseases and conditions that are beneficially treated bycompounds that block the endothelin signaling pathway that leads tovasoconstriction and in particular those diseases or conditionsbeneficially treated by endothelin receptor antagonists.

Bosentan is known by the chemical namesN-[6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-pyrimidin-2-yl-pyrimidin-4-yl]-4-tert-butyl-benzenesulfonamideand4-tert-butyl-N-[6-(2-hydroxy-ethoxy)-5-(2-methoxy-phenoxy)-[2,2′]-bipyrimidin-4-yl]-benzenesulfonamide.

Bosentan is a tetrasubstituted pyrimidine derivative that was reportedin U.S. Pat. No. 5,292,740 to be useful for treating circulatorydisorders, such as hypertension. Bosentan is now known to be a dualendothelin receptor antagonist that blocks the binding of endothelin toboth the ET_(A) and ET_(B) receptors.

Endothelin-1 (ET-1), a 21-amino acid peptide neurohormone, was firstisolated and described in 1998 and is an extremely potent andlong-acting vasoconstrictor (Itoh, Y et al, FEBS Lett 1988, 231:440).ET-1 causes vasoconstriction by binding to ET_(A) and ET_(B), which arereceptors in the endothelium and vascular smooth muscle. ET-1 levels areelevated in the plasma and lung tissue of patients with pulmonaryarterial hypertension, which suggests that ET-1 has a pathogenic role inthis disease. Bosentan is believed to work by competitively andspecifically binding to ET_(A) and ET_(B) receptor sites in theendothelium and vascular smooth muscle with a slightly higher affinityfor ET_(A) than for ET_(B). This binding inhibits ET-1 from binding toET_(A) and/or ET_(B), which interferes with a signaling pathway that isresponsible for causing vasoconstriction.

Bosentan has been approved by the Food and Drug Administration to treatthe symptoms of pulmonary arterial hypertension, high blood pressurewithin the main artery that carries blood from the heart's rightventricle to the lungs. Bosentan has been shown to be effective indecreasing the constriction this artery, thereby increasing the supplyof blood to the lungs and reducing the workload incurred by the heart.

Bosentan has been reported to have a half-life in humans ofapproximately five hours and is eliminated mainly through hepaticmetabolism, followed by biliary excretion of three metabolites (seeCenter for Drug Evaluation and Research Approval Package for ApplicationNumber 21-290; Clinical Pharmacology and Biopharmaceutics Review; Aug.16, 2001). One of these metabolites, hydroxybosentan, is active andresponsible for up to 20% of the overall pharmaceutical properties ofbosentan.

Bosentan is typically administered twice per day due to its shorthalf-life. Multiple dosing can lead to compliance problems such asmissed doses and overdosing when compensating for missed doses.Moreover, bosentan may cause liver damage due to bilary excretion andbirth defects if taken during pregnancy. Thus, bosentan cannot be safelyadministered to patients who are pregnant or who suffer from liverimpairment. Less serious side-effects of bosentan include headache,nasopharyngitis, flushing, edema of the lower limbs, hypotension, andpalpitations. Bosentan may also decrease the effectiveness of hormonalcontraceptives, regardless of the route of administration. Bosentan mayalso irreversibly lower sperm count in some men. These side effects maybe attributable to one or more of the metabolites of bosentan and/oroverdosing due to poor compliance.

Despite the beneficial activities of bosentan, there is a continuingneed for new compounds to treat the aforementioned diseases andconditions.

SUMMARY OF THE INVENTION

This invention relates to novel endothelin receptor antagonists,derivatives, and pharmaceutically acceptable acid addition saltsthereof. The invention also provides compositions comprising a compoundof this invention and the use of such compositions in methods oftreating diseases and conditions that are beneficially treated bycompounds that block the endothelin signaling pathway that leads tovasoconstriction and in particular those diseases or conditionsbeneficially treated by endothelin receptor antagonists.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The terms “ameliorate” and “treat” are used interchangeably and includeboth therapeutic treatment and prophylactic treatment (reducing thelikelihood of development). Both terms mean decrease, suppress,attenuate, diminish, arrest, or stabilize the development or progressionof a disease (e.g., a disease or disorder delineated herein), lessen theseverity of the disease or improve the symptoms associated with thedisease.

By “disease” is meant any condition or disorder that damages orinterferes with the normal function of a cell, tissue, or organ.

It will be recognized that some variation of natural isotopic abundanceoccurs in a synthesized compound depending upon the origin of chemicalmaterials used in the synthesis. Thus, a preparation of bosentan willinherently contain small amounts of deuterated isotopologues. Theconcentration of naturally abundant stable hydrogen isotopes,notwithstanding this variation, is small and immaterial with respect tothe degree of stable isotopic substitution of compounds of thisinvention. See for instance Wada E et al., Seikagaku 1994, 66:15; GanesL Z et al., Comp Biochem Physiol Mol Integr Physiol 1998, 119:725. In acompound of this invention, when a particular position is designated ashaving deuterium, it is understood that the abundance of deuterium atthat position is substantially greater than the natural abundance ofdeuterium, which is 0.015%. A position designated as having deuteriumtypically has a minimum isotopic enrichment factor of at least 3000 (45%deuterium incorporation) at each atom designated as deuterium in saidcompound.

The term “isotopic enrichment factor” as used herein means the ratiobetween the isotopic abundance and the natural abundance of a specifiedisotope.

In other embodiments, a compound of this invention has an isotopicenrichment factor for each deuterium present at a site designated as apotential site of deuteration on the compound of at least 1000 (15%deuterium incorporation), at least 1500 (22.5% deuterium incorporation),at least 2000 (30% deuterium incorporation), at least 2500 (37.5%deuterium incorporation), at least 3000 (45% deuterium incorporation),at least 3500 (52.5% deuterium incorporation), at least 4000 (60%deuterium incorporation), at least 4500 (67.5% deuterium incorporation),at least 5000 (75% deuterium), at least 5500 (82.5% deuteriumincorporation), at least 6000 (90% deuterium incorporation), at least6333.3 (95% deuterium incorporation), at least 6466.7 (97% deuteriumincorporation), at least 6600 (99% deuterium incorporation), or at least6633.3 (99.5% deuterium incorporation). It is understood that theisotopic enrichment factor of each deuterium present at a sitedesignated as a site of deuteration is independent of other deuteratedsites. For example, if there are two sites of deuteration on a compoundone site could be deuterated at 22.5% while the other could bedeuterated at 37.5% and still be considered a compound wherein theisotopic enrichment factor is at least 1500 (22.5%).

In some embodiment, a compound of the invention, contains less than 10%,preferably less than 6%, and more preferably less than 3% of all otherisotopologues combined, including a form that lacks any deuterium. Incertain aspects, the compound contains less than “X”% of all otherisotopologues combined, including a form that lacks any deuterium; whereX is any number between 0 and 10 (e.g., 1, 0.5, 0.001) inclusive.Compositions of matter that contain greater than 10% of all otherisotopologues combined are referred to herein as “mixtures” and mustmeet the parameters set forth below. These limits of isotopiccomposition and all references to isotopic composition herein, refersolely to the relative amounts of deuterium/hydrogen present in theactive, free base form of the compound of Formula I, and neitherincludes the isotopic composition of counterions, or of any other atoms.

In the compounds of this invention any atom not specifically designatedas a particular isotope is meant to represent any stable isotope of thatatom. Unless otherwise stated, when a position is designatedspecifically as “H” or “hydrogen”, the position is understood to havehydrogen at its natural abundance isotopic composition.

The term “isotopologue” refers to a species that differs from a specificcompound of this invention only in the isotopic composition thereof orof its ions.

The term “compound,” as used herein, is also intended to includesolvates or hydrates thereof.

A salt of a compound of this invention is formed between an acid and abasic group of the compound, such as an amino functional group or a baseand an acidic group of the compound, such as a carboxyl functionalgroup. According to another embodiment, the compound is apharmaceutically acceptable acid addition salt.

The term “pharmaceutically acceptable,” as used herein, refers to acomponent that is, within the scope of sound medical judgment, suitablefor use in contact with the tissues of humans and other mammals withoutundue toxicity, irritation, allergic response and the like, and arecommensurate with a reasonable benefit/risk ratio. A “pharmaceuticallyacceptable salt” means any non-toxic salt that, upon administration to arecipient, is capable of providing, either directly or indirectly, acompound or a prodrug of a compound of this invention. A“pharmaceutically acceptable counterion” is an ionic portion of a saltthat is not toxic when released from the salt upon administration to arecipient.

Acids commonly employed to form pharmaceutically acceptable saltsinclude inorganic acids such as hydrogen bisulfide, hydrochloric acid,hydrobromic acid, hydroiodic acid, sulfuric acid and phosphoric acid, aswell as organic acids such as para-toluenesulfonic acid, salicylic acid,tartaric acid, bitartaric acid, ascorbic acid, maleic acid, besylicacid, fumaric acid, gluconic acid, glucuronic acid, formic acid,glutamic acid, methanesulfonic acid, ethanesulfonic acid,benzenesulfonic acid, lactic acid, oxalic acid, para-bromophenylsulfonicacid, carbonic acid, succinic acid, citric acid, benzoic acid and aceticacid, as well as related inorganic and organic acids. Suchpharmaceutically acceptable salts thus include sulfate, pyrosulfate,bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate,dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide,iodide, acetate, propionate, decanoate, caprylate, acrylate, formate,isobutyrate, caprate, heptanoate, propiolate, oxalate, malonate,succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate,hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate,dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate,terephthalate, sulfonate, xylenesulfonate, phenylacetate,phenylpropionate, phenylbutyrate, citrate, lactate, β-hydroxybutyrate,glycolate, maleate, tartrate, methanesulfonate, propanesulfonate,naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate and othersalts. In one embodiment, pharmaceutically acceptable acid additionsalts include those formed with mineral acids such as hydrochloric acidand hydrobromic acid, and especially those formed with organic acidssuch as maleic acid.

As used herein, the term “hydrate” means a compound which furtherincludes a stoichiometric or non-stoichiometric amount of water bound bynon-covalent intermolecular forces.

As used herein, the term “solvate” means a compound which furtherincludes a stoichiometric or non-stoichiometric amount of solvent suchas water, acetone, ethanol, methanol, dichloromethane, 2-propanol, orthe like, bound by non-covalent intermolecular forces.

The compounds of the present invention may contain one or moreasymmetric carbon atoms. As such, a compound of this invention can existas the individual stereoisomers (enantiomers or diastereomers) as well amixture of any possible stereoisomers. Accordingly, a compound of thepresent invention will include not only a stereoisomeric mixture, butalso individual respective stereoisomers that are substantially freefrom other stereoisomers. The term “substantially free of otherstereoisomers” as used herein means less than 25% of otherstereoisomers, preferably less than 10% of other stereoisomers, morepreferably less than 5% of other stereoisomers and most preferably lessthan 2% of other stereoisomers, or less than “X”% of other stereoisomers(wherein X is a number between 0 and 100, inclusive) are present.Methods of obtaining or synthesizing diastereomers are well known in theart and may be applied as practicable to final compounds or to startingmaterial or intermediates. Other embodiments are those wherein thecompound is an isolated compound. The term “at least X %enantiomerically enriched” as used herein means that at least X % of thecompound is a single enantiomeric form, wherein X is a number between 0and 100, inclusive.

The term “stable compounds”, as used herein, refers to compounds whichpossess stability sufficient to allow for their manufacture and whichmaintain the integrity of the compound for a sufficient period of timeto be useful for the purposes detailed herein (e.g., formulation intotherapeutic products, intermediates for use in production of therapeuticcompounds, isolatable or storable intermediate compounds, treating adisease or condition responsive to therapeutic agents).

“D” refers to deuterium. “Stereoisomer” refers to both enantiomers anddiastereomers. “tert” refers to tertiary. “^(t)Bu” refers to t-butyl.

Throughout this specification, a variable may be referred to generally(e.g., “each Y”) or may be referred to specifically (e.g., Y^(1a),Y^(1b), Y^(1c), Y^(2a), Y^(2b), Y^(2c), Y^(2d), etc.). Unless otherwiseindicated, when a variable is referred to generally, it is meant toinclude all specific embodiments of that particular variable.

Therapeutic Compounds

The present invention provides a compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein:

each Y is independently selected from hydrogen or deuterium, and Y^(2a)is additionally selected from OH;

each Z is independently selected from hydrogen, deuterium, or fluorine;and

-   -   at least one Y or Z is deuterium.

In one embodiment, each Y is the same. In a more specific embodiment,Y^(1a), Y^(1b) and Y^(1c) are simultaneously deuterium.

In another embodiment, Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g),Y^(2h), Y^(2i) are the same. In still another embodiment, Y^(2a),Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h), Y^(2i) are thesame.

In another embodiment, Y^(1a), Y^(1b) and Y^(1c) are simultaneouslydeuterium and Y^(2a), Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g),Y^(2h), Y^(2i) are simultaneously hydrogen.

In another embodiment, Y^(1a), Y^(1b) and Y^(1c) are simultaneouslydeuterium; Y^(2a) is OH; and Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f),Y^(2g), Y^(2h), Y^(2i) are simultaneously hydrogen.

In another embodiment, Y^(2a), Y^(2b) and Y^(2c) are simultaneouslydeuterium.

In another embodiment, Y^(2b) and Y^(2c) are simultaneously deuterium;and Y^(2a) is OH.

In another embodiment, Y^(2a), Y^(2b), Y^(2c) Y^(2d), Y^(2e) and Y^(2f)are simultaneously deuterium.

In another embodiment, Y^(2b), Y^(2c) Y^(2d), Y^(2e) and Y^(2f) aresimultaneously deuterium; and Y^(2a) is OH.

In another embodiment, Y^(2a), Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f),Y^(2g), Y^(2h), Y^(2i) are simultaneously deuterium.

In another embodiment, Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g),Y^(2h), Y^(2i) are simultaneously deuterium; and Y^(2a) is OH.

In another embodiment, each Z is the same.

In another embodiment each of Z^(1a) and Z^(1b) are independentlyselected from fluorine or deuterium. In a more specific embodiment,Z^(1a) and Z^(1b) are simultaneously deuterium.

In another embodiment, each Y¹ is the same, each of Y^(2b), Y^(2c)Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h), Y^(2i) is the same; each Z isthe same, and the compound (Cmpd) is selected from any one of thecompounds described in Table 1 (below).

TABLE 1 Description of Exemplary Compounds of This Invention Cmpd EachY¹ Y^(2a) Y^(2b)-Y^(2i) Each Z 100 D H H D 101 D D D H 102 D H H H 103 HD D H 104 H H H D 105 H D D D 106 D D D D 107 D OH H D 108 D OH D H 109D OH H H 110 H OH D H 111 H OH H D 112 H OH D D 113 D OH D D 114 D H H F115 D D D F 116 H D D F 117 D OH H F 118 D OH D F 119 H OH D F

In another set of embodiments, any atom not designated as deuterium inany of the embodiments set forth above is present at its naturalisotopic abundance.

In an even more specific embodiment, the compound of Formula I isselected from:

The synthesis of compounds of the formulae herein (e.g., Formula I) canbe readily achieved by synthetic chemists of ordinary skill. Relevantprocedures and intermediates are disclosed, for instance, in U.S. Pat.Nos. 5,292,740 and 6,139,971; PCT patent publication WO2001005120; andHarrington, P J et al, Org Process Res Dev, 6(2): 120. Such methods canbe carried out utilizing corresponding deuterated reagents to synthesizethe compounds delineated herein, or invoking standard syntheticprotocols known in the art for introducing isotopic atoms to a chemicalstructure.

Exemplary Synthesis

A convenient method for producing compounds of the formulae herein(e.g., Formula I) is illustrated in Scheme 1.

The exemplary synthesis depicted in Scheme 1 involves condensation of2-chloromalonic acid dimethyl ester 11 with an appropriately deuteratedguaiacol 10 to afford the 2-(2-methoxyphenoxy)malonic acid dimethylester 12, followed by cyclization of 12 with 13 to afford thecorresponding bipyrimidinedione 14. This compound 14 is treated withrefluxing POCl₃ to afford the dichlorobipyrimidine 15, which issubsequently treated with an appropriately deuterated4-tert-butylphenylsulfonamide 16, K₂CO₃ and tetrabutylammonium bromide(TBAB) in toluene to provide the monosubstituted sulfonamide 17.Compound 17 is thereafter treated with an appropriately deuterated orfluorinated ethyleneglycol mono-tert-butyl ether 18 and NaOH in hottoluene to afford the tert-butyl ether protected intermediate, which isthereafter deprotected by reaction with formic acid to afford theformate ester. This ester is then hydrolyzed with NaOH in a mixture ofwater and ethanol, to afford the target compounds of Formula I. Suchcompounds of Formula I are readily purified by crystallization,comprising heating the crude product into a mixture of ethanol and waterto afford a solution and thereafter allowing the solution to cool. Otherapproaches to synthesizing compounds of the formulae herein (e.g.,Formula I) can readily be adapted from references cited herein.Variations of these procedures and their optimization are within theskill of the ordinary practitioner.

An appropriately deuterated 4-tert-butylphenylsulfonamide 16 can besynthesized as in Scheme 2.

An appropriately deuterated tert-butanol 19, such as commerciallyavailable d9-tert-butanol, is reacted with benzene in the presence offerric chloride (see Potts, W M et al, J Am Chem Soc 1939, 61:2553) toprovide 20, which is then reacted with chlorosulfonic acid to providethe sulfonyl chloride 21 (Gayen, S et al, Internet Electronic J MolDesign 2005, 4:556). The sulfonyl chloride is converted to thesulfonamide 16 according to the method of Morimoto, H et al, J Med Chem,2001, 44:3355. Although not shown in Scheme 2, the sulfonic acid analogof compound 21 (compound 23) is readily available via hydrolysis of 21in aqueous dioxane according to the method of Tonnet, M L et al, Aus JChem 1971, 24:703.

An appropriately deuterated ethyleneglycol mono-tert-butyl ether 18 maybe prepared as shown in Scheme 3.

Commercially available 2-tert-butoxyacetic acid (22) is reduced withd3-borane according to the method of Yoon, N M et al., J Org Chem 1973,38:2786 to produce the corresponding deuterated ethyleneglycolmono-tert-butyl ether 18.

An alternate route to a compound of formula I, wherein each Z isdeuterium is shown in Scheme 4.

The appropriately deuterated sulfonamide 17 from Scheme 1 is treatedwith ethyl 2-hydroxyacetate (24) to produce the corresponding ester 25according to the method of Harada, H et al, Chem Pharm Bull 2001,49:606-612. The ester 25 is hydrolyzed to the corresponding acid 26,which is then reduced with deuterodiborane in THF to the deuteratedcompound of Formula I. Alternatively, the ester 25 may be reduceddirectly to the deuterated compound of formula I by treatment withLiAlD₄.

Certain intermediates that are useful for preparing compounds of FormulaI are new. Accordingly, other embodiments of this invention relate to acompound of any one of formulae 12, 14, 15, 16, 17, 18, 21 or 23 shownin Schemes 1-3.

The specific approaches and compounds shown above are not intended to belimiting. The chemical structures in the schemes herein depict variablesthat are hereby defined commensurately with chemical group definitions(moieties, atoms, etc.) of the corresponding position in the compoundformulae herein, whether identified by the same variable name (e.g.,Y^(1a), Y^(1b), Y^(1c), Y^(2a), Y^(2b), Y^(2c), Y^(2d), Y^(2e), Y^(2f),Y^(2g), Y^(2h), Y^(2i), Z^(1a) and Z^(1b)) or not. The suitability of achemical group in a compound structure for use in synthesis of anothercompound structure is within the knowledge of one of ordinary skill inthe art.

Additional methods of synthesizing compounds of the formulae herein(e.g., Formula I) and their synthetic precursors, including those withinroutes not explicitly shown in schemes herein, are within the means ofchemists of ordinary skill in the art. Synthetic chemistrytransformations and protecting group methodologies (protection anddeprotection) useful in synthesizing the applicable compounds are knownin the art and include, for example, those described in R. Larock,Comprehensive Organic Transformations, VCH Publishers (1989); T. W.Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, 3^(rd)Ed., John Wiley and Sons (1999); L. Fieser and M. Fieser, Fieser andFieser's Reagents for Organic Synthesis, John Wiley and Sons (1994); andL. Paquette, ed., Encyclopedia of Reagents for Organic Synthesis, JohnWiley and Sons (1995) and subsequent editions thereof.

Combinations of substituents and variables envisioned by this inventionare only those that result in the formation of stable compounds.

The invention further provides a mixture of a compound of this inventionand its lighter isotopologues. These mixtures may occur, for instance,simply as the result of an inefficiency of incorporating the isotope ata given position; intentional or inadvertent exchange of protons fordeuterium, e.g. exchange of bulk solvent for heteroatom-attacheddeuterium; or intentional mixtures of pure compounds.

In one embodiment, such mixtures comprise at least about 50% of theheavy atom isotopic compound (i.e., less than about 50% of lighterisotopologues). More preferable is a mixture comprising at least 80% ofthe heavy atom isotopic compound. Most preferable is a mixturecomprising 90% of the heavy atom isotopic compound. In one aspect, is amixture at least about “X”% of the heavy atom isotopic compound (i.e.,less than about X % of lighter isotopologues), where X is a numberbetween 0 and 100, inclusive.

Compositions

The invention also provides compositions comprising an effective amountof a compound of Formula I (e.g., including any of the formulae herein),or a pharmaceutically acceptable salt thereof, and an acceptablecarrier. Preferably, a composition of this invention is formulated forpharmaceutical use (“a pharmaceutical composition”), wherein the carrieris a pharmaceutically acceptable carrier. The carrier(s) must be“acceptable” in the sense of being compatible with the other ingredientsof the formulation and, in the case of a pharmaceutically acceptablecarrier, not deleterious to the recipient thereof in amounts typicallyused in medicaments.

Pharmaceutically acceptable carriers, adjuvants and vehicles that may beused in the pharmaceutical compositions of this invention include, butare not limited to, ion exchangers, alumina, aluminum stearate,lecithin, serum proteins, such as human serum albumin, buffer substancessuch as phosphates, glycine, sorbic acid, potassium sorbate, partialglyceride mixtures of saturated vegetable fatty acids, water, salts orelectrolytes, such as protamine sulfate, disodium hydrogen phosphate,potassium hydrogen phosphate, sodium chloride, zinc salts, colloidalsilica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-basedsubstances, polyethylene glycol, sodium carboxymethylcellulose,polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers,polyethylene glycol and wool fat.

If required, the solubility and bioavailability of the compounds of thepresent invention in pharmaceutical compositions may be enhanced bymethods well-known in the art. One method includes the use of lipidexcipients in the formulation. See “Oral Lipid-Based Formulations:Enhancing the Bioavailability of Poorly Water-Soluble Drugs (Drugs andthe Pharmaceutical Sciences),” David J. Hauss, ed. Informa Healthcare,2007; and “Role of Lipid Excipients in Modifying Oral and ParenteralDrug Delivery: Basic Principles and Biological Examples,” Kishor M.Wasan, ed. Wiley-Interscience, 2006.

Another known method of enhancing bioavailability is the use of anamorphous form of a compound of this invention optionally formulatedwith a poloxamer, such as LUTROL™ and PLURONIC™ (BASF Corporation), orblock copolymers of ethylene oxide and propylene oxide. See U.S. Pat.No. 7,014,866; and United States patent publications 20060094744 and20060079502.

The pharmaceutical compositions of the invention include those suitablefor oral, rectal, nasal, topical (including buccal and sublingual),vaginal or parenteral (including subcutaneous, intramuscular,intravenous and intradermal) administration. In certain embodiments, thecompound of the formulae herein is administered transdermally (e.g.,using a transdermal patch or iontophoretic techniques). Otherformulations may conveniently be presented in unit dosage form, e.g.,tablets, sustained release capsules, and in liposomes, and may beprepared by any methods well known in the art of pharmacy. See, forexample, Remington's Pharmaceutical Sciences, Mack Publishing Company,Philadelphia, Pa. (17th ed. 1985).

Such preparative methods include the step of bringing into associationwith the molecule to be administered ingredients such as the carrierthat constitutes one or more accessory ingredients. In general, thecompositions are prepared by uniformly and intimately bringing intoassociation the active ingredients with liquid carriers, liposomes orfinely divided solid carriers, or both, and then, if necessary, shapingthe product.

In certain embodiments, the compound is administered orally.Compositions of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, sachets, or tabletseach containing a predetermined amount of the active ingredient; apowder or granules; a solution or a suspension in an aqueous liquid or anon-aqueous liquid; an oil-in-water liquid emulsion; a water-in-oilliquid emulsion; packed in liposomes; or as a bolus, etc. Soft gelatincapsules can be useful for containing such suspensions, which maybeneficially increase the rate of compound absorption.

In the case of tablets for oral use, carriers that are commonly usedinclude lactose and corn starch. Lubricating agents, such as magnesiumstearate, are also typically added. For oral administration in a capsuleform, useful diluents include lactose and dried cornstarch. When aqueoussuspensions are administered orally, the active ingredient is combinedwith emulsifying and suspending agents. If desired, certain sweeteningand/or flavoring and/or coloring agents may be added.

Compositions suitable for oral administration include lozengescomprising the ingredients in a flavored basis, usually sucrose andacacia or tragacanth; and pastilles comprising the active ingredient inan inert basis such as gelatin and glycerin, or sucrose and acacia.

Compositions suitable for parenteral administration include aqueous andnon-aqueous sterile injection solutions which may contain anti-oxidants,buffers, bacteriostats and solutes which render the formulation isotonicwith the blood of the intended recipient; and aqueous and non-aqueoussterile suspensions which may include suspending agents and thickeningagents. The formulations may be presented in unit-dose or multi-dosecontainers, for example, sealed ampules and vials, and may be stored ina freeze dried (lyophilized) condition requiring only the addition ofthe sterile liquid carrier, for example water for injections,immediately prior to use. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules and tablets.

Such injection solutions may be in the form, for example, of a sterileinjectable aqueous or oleaginous suspension. This suspension may beformulated according to techniques known in the art using suitabledispersing or wetting agents (such as, for example, Tween 80) andsuspending agents. The sterile injectable preparation may also be asterile injectable solution or suspension in a non-toxicparenterally-acceptable diluent or solvent, for example, as a solutionin 1,3-butanediol. Among the acceptable vehicles and solvents that maybe employed are mannitol, water, Ringer's solution and isotonic sodiumchloride solution. In addition, sterile, fixed oils are conventionallyemployed as a solvent or suspending medium. For this purpose, any blandfixed oil may be employed including synthetic mono- or diglycerides.Fatty acids, such as oleic acid and its glyceride derivatives are usefulin the preparation of injectables, as are naturalpharmaceutically-acceptable oils, such as olive oil or castor oil,especially in their polyoxyethylated versions. These oil solutions orsuspensions may also contain a long-chain alcohol diluent or dispersant.

The pharmaceutical compositions of this invention may be administered inthe form of suppositories for rectal administration. These compositionscan be prepared by mixing a compound of this invention with a suitablenon-irritating excipient which is solid at room temperature but liquidat the rectal temperature and therefore will melt in the rectum torelease the active components. Such materials include, but are notlimited to, cocoa butter, beeswax and polyethylene glycols.

The pharmaceutical compositions of this invention may be administered bynasal aerosol or inhalation. Such compositions are prepared according totechniques well-known in the art of pharmaceutical formulation and maybe prepared as solutions in saline, employing benzyl alcohol or othersuitable preservatives, absorption promoters to enhance bioavailability,fluorocarbons, and/or other solubilizing or dispersing agents known inthe art. See, e.g.: Rabinowitz J D and Zaffaroni A C, U.S. Pat. No.6,803,031, assigned to Alexza Molecular Delivery Corporation.

Topical administration of the pharmaceutical compositions of thisinvention is especially useful when the desired treatment involves areasor organs readily accessible by topical application. For topicalapplication to the skin, the pharmaceutical composition should beformulated with a suitable ointment containing the active componentssuspended or dissolved in a carrier. Carriers for topical administrationof the compounds of this invention include, but are not limited to,mineral oil, liquid petroleum, white petroleum, propylene glycol,polyoxyethylene polyoxypropylene compound, emulsifying wax, and water.Alternatively, the pharmaceutical composition can be formulated with asuitable lotion or cream containing the active compound suspended ordissolved in a carrier. Suitable carriers include, but are not limitedto, mineral oil, sorbitan monostearate, polysorbate 60, cetyl esterswax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol, and water. Thepharmaceutical compositions of this invention may also be topicallyapplied to the lower intestinal tract by rectal suppository formulationor in a suitable enema formulation. Topically-transdermal patches andiontophoretic administration are also included in this invention.

Application of the subject therapeutics may be local, so as to beadministered at the site of interest. Various techniques can be used forproviding the subject compositions at the site of interest, such asinjection, use of catheters, trocars, projectiles, pluronic gel, stents,sustained drug release polymers or other device which provides forinternal access.

Thus, according to yet another embodiment, the compounds of thisinvention may be incorporated into compositions for coating animplantable medical device, such as prostheses, artificial valves,vascular grafts, stents, or catheters. Suitable coatings and the generalpreparation of coated implantable devices are known in the art and areexemplified in U.S. Pat. Nos. 6,099,562; 5,886,026; and 5,304,121. Thecoatings are typically biocompatible polymeric materials such as ahydrogel polymer, polymethyldisiloxane, polycaprolactone, polyethyleneglycol, polylactic acid, ethylene vinyl acetate, and mixtures thereof.The coatings may optionally be further covered by a suitable topcoat offluorosilicone, polysaccharides, polyethylene glycol, phospholipids orcombinations thereof to impart controlled release characteristics in thecomposition. Coatings for invasive devices are to be included within thedefinition of pharmaceutically acceptable carrier, adjuvant or vehicle,as those terms are used herein.

According to another embodiment, the invention provides a method ofcoating an implantable medical device comprising the step of contactingsaid device with the coating composition described above. It will beobvious to those skilled in the art that the coating of the device willoccur prior to implantation into a mammal.

According to another embodiment, the invention provides a method ofimpregnating an implantable drug release device comprising the step ofcontacting said drug release device with a compound or composition ofthis invention. Implantable drug release devices include, but are notlimited to, biodegradable polymer capsules or bullets, non-degradable,diffusible polymer capsules and biodegradable polymer wafers.

According to another embodiment, the invention provides an implantablemedical device coated with a compound or a composition comprising acompound of this invention, such that said compound is therapeuticallyactive.

According to another embodiment, the invention provides an implantabledrug release device impregnated with or containing a compound or acomposition comprising a compound of this invention, such that saidcompound is released from said device and is therapeutically active.

Where an organ or tissue is accessible because of removal from thepatient, such organ or tissue may be bathed in a medium containing acomposition of this invention, a composition of this invention may bepainted onto the organ, or a composition of this invention may beapplied in any other convenient way.

In another embodiment, a composition of the present invention furthercomprises a second therapeutic agent. The second therapeutic agentincludes any compound or therapeutic agent known to have or thatdemonstrates advantageous properties when administered with anendothelin antagonist. Such agents are the same as those indicated asuseful in combination with bosentan, including, but not limited to thosedescribed in U.S. Pat. Nos. 6,635,648; 6,586,391; 6,869,970; 5,945,448;and 5,696,116; and in PCT patent publications WO 2005101608; WO2004082637; WO 2004017993; and WO 2002074034. Preferably, the secondtherapeutic agent is an agent useful in the treatment or prevention of adisease or condition selected from pulmonary arterial hypertension,erectile dysfunction, chronic obstructive pulmonary disease, chronicpelvic pain syndrome type III, primary dysmenorrhea, pre-eclampsia,thalassemia, skin fibrosis, hypertension, hypoxia-induced pulmonaryartery hypertension, interstitial lung disease, scleroderma, idiopathicpulmonary fibrosis, pulmonary hypertension, chronic thromboembolicpulmonary hypertension, Eisenmenger's syndrome, benign prostatichyperplasia, high blood pressure, coronary disorders, cardiacinsufficiency, renal cerebral ischemia, cardiac infarct, migraine,subarachnoid haemorrhage, Raynaud syndrome, skin cancer,atherosclerosis, sickle cell disease, digital ulcers, and others,including, but not limited to those disclosed in U.S. Pat. No.6,635,648; U.S. Pat. No. 5,292,740; U.S. Pat. No. 6,586,391; U.S. Pat.No. 6,869,970; U.S. Pat. No. 5,945,448; U.S. Pat. No. 5,696,116; WO2005101608; WO 2004082637; WO 2004017993; WO 2002074034; and WO9638173A1.

In one embodiment, the second therapeutic agent is selected from aprostacyclin, a prostacyclin derivative, a second endothelin antagonist,a dopaminergic agonist, a phosphodiesterase inhibitor, a sympatheticnervous system antagonist, an inhibitor of endothelin converting enzyme,an antihypertensive, an alpha-adrenergic blocker, or an angiotensin IIreceptor antagonist.

In another embodiment, the second therapeutic agent is selected from aphosphodiesterase inhibitor, such as sildenafil.

In another embodiment, the second therapeutic agent is selected from aprostacyclin or prostacyclin derivative, such as epoprostenol,treprostinil, iloprost, or beraprost.

In another embodiment, the invention provides separate dosage forms of acompound of this invention and a second therapeutic agent that areassociated with one another. The term “associated with one another” asused herein means that the separate dosage forms are packaged togetheror otherwise attached to one another such that it is readily apparentthat the separate dosage forms are intended to be sold and administeredtogether (within less than 24 hours of one another, consecutively orsimultaneously).

In the pharmaceutical compositions of the invention, the compound of thepresent invention is present in an effective amount. As used herein, theterm “effective amount” refers to an amount which, when administered ina proper dosing regimen, is sufficient to treat (therapeutically orprophylactically) the target disorder. For example, and effective amountis sufficient to reduce or ameliorate the severity, duration orprogression of the disorder being treated, prevent the advancement ofthe disorder being treated, cause the regression of the disorder beingtreated, or enhance or improve the prophylactic or therapeutic effect(s)of another therapy.

The interrelationship of dosages for animals and humans (based onmilligrams per meter squared of body surface) is described in Freireichet al., (1966) Cancer Chemother. Rep 50: 219. Body surface area may beapproximately determined from height and weight of the patient. See,e.g., Scientific Tables, Geigy Pharmaceuticals, Ardsley, N.Y., 1970,537. An effective amount of a compound of this invention to beadministered to a normal adult human can range from about 1 mg to about1000 mg/day, more preferably from about 5 mg to about 500 mg/day, morepreferably from about 25 mg/ to about 250 mg/day. Daily amounts of acompound of this invention will be administered in from one to aboutnine unit dosages per day. Effective doses will also vary, as recognizedby those skilled in the art, depending on the diseases treated, theseverity of the disease, the route of administration, the sex, age andgeneral health condition of the patient, excipient usage, thepossibility of co-usage with other therapeutic treatments such as use ofother agents and the judgment of the treating physician.

For pharmaceutical compositions that comprise a second therapeuticagent, an effective amount of the second therapeutic agent is betweenabout 20% and 100% of the dosage normally utilized in a monotherapyregime using just that agent. Preferably, an effective amount is betweenabout 70% and 100% of the normal monotherapeutic dose. The normalmonotherapeutic dosages of these second therapeutic agents are wellknown in the art. See, e.g., Wells et al., eds., PharmacotherapyHandbook, 2nd Edition, Appleton and Lange, Stamford, Conn. (2000); PDRPharmacopoeia, Tarascon Pocket Pharmacopoeia 2000, Deluxe Edition,Tarascon Publishing, Loma Linda, Calif. (2000), each of which referencesare incorporated herein by reference in their entirety.

It is expected that some of the second therapeutic agents referencedabove will act synergistically with the compounds of this invention.When this occurs, it will allow the effective dosage of the secondtherapeutic agent and/or the compound of this invention to be reducedfrom that required in a monotherapy. This has the advantage ofminimizing toxic side effects of either the second therapeutic agent ofa compound of this invention, synergistic improvements in efficacy,improved ease of administration or use and/or reduced overall expense ofcompound preparation or formulation.

Methods of Treatment

According to another embodiment, the invention provides a method oftreating a disease that is beneficially treated by bosentan comprisingthe step of administering to a subject in need thereof an effectiveamount of a compound or a composition of this invention. Such conditionsand diseases are well known in the art and include but are not limitedto pulmonary arterial hypertension, erectile dysfunction, chronicobstructive pulmonary disease, chronic pelvic pain syndrome type III,primary dysmenorrhea, pre-eclampsia, thalassemia, skin fibrosis,hypertension, hypoxia-induced pulmonary artery hypertension,interstitial lung disease, scleroderma, idiopathic pulmonary fibrosis,pulmonary hypertension, chronic thromboembolic pulmonary hypertension,Eisenmenger's syndrome, benign prostatic hyperplasia, high bloodpressure, coronary disorders, cardiac insufficiency, renal cerebralischemia, cardiac infarct, migraine, subarachnoid haemorrhage, Raynaudsyndrome, skin cancer, atherosclerosis, sickle cell disease, and digitalulcers.

In a more specific embodiment, the method of this invention is used totreat a disease or condition selected from pulmonary arterialhypertension, erectile dysfunction, skin fibrosis, interstitial lungdisease, scleroderma, chronic thromboembolic pulmonary hypertension,Eisenmenger's syndrome, skin cancer, sickle cell disease, digitalulcers.

In an even more specific embodiment, the method of this invention isused to treat a disease or condition selected from pulmonaryhypertension (including pediatric subjects, subjects with class IIdisease who are mildly symptomatic, patients with sickle cell anemia,and patients with chronic thromboembolic pulmonary hypertension),idiopathic pulmonary fibrosis, digital ulcerations in patients withscleroderma, and interstitial lung disease in patients with scleroderma.

Methods delineated herein include those wherein the subject isidentified as in need of a particular stated treatment. Identifying asubject in need of such treatment can be in the judgment of a subject ora health care professional and can be subjective (e.g. opinion) orobjective (e.g. measurable by a test or diagnostic method).

In another embodiment, the invention provides a method of modulating theinteraction between ET-1 and its receptors in a cell, said modulationcomprising contacting a cell with one or more compounds of any of theformulae herein.

In another embodiment, the above method of treatment comprises thefurther step of co-administering to the patient one or more secondtherapeutic agents. The choice of second therapeutic agent may be madefrom any second therapeutic agent known to be useful forco-administration with bosentan. Examples of such agents and theconditions and diseases for which each may be used in conjunction with acompound of this invention are described in PCT publications WO04017993A1 and WO 9638173A1. Preferably, the second therapeutic agent isan agent useful in the treatment or prevention of a disease or conditionselected from pulmonary arterial hypertension, brain edema orEisenmenger's syndrome.

In one embodiment, the second therapeutic agent is selected from aprostacyclin or a prostacyclin analogue and the condition treated ispulmonary arterial hypertension. In a more specific embodiment, theprostacyclin or prostacyclin analogue is selected from epoprostenol,treprostinil, iloprost, or beraprost.

In another embodiment, the second therapeutic agent is aphosphodiesterase V inhibitor and the condition treated is selected frompulmonary arterial hypertension and Eisenmenger's syndrome. In a morespecific embodiment, the phosphodiesterase V inhibitor is sildenafil.

The term “co-administered” as used herein means that the secondtherapeutic agent may be administered together with a compound of thisinvention as part of a single dosage form (such as a composition of thisinvention comprising a compound of the invention and an secondtherapeutic agent as described above) or as separate, multiple dosageforms. Alternatively, the additional agent may be administered prior to,consecutively with, or following the administration of a compound ofthis invention. In such combination therapy treatment, both thecompounds of this invention and the second therapeutic agent(s) areadministered by conventional methods. The administration of acomposition of this invention comprising both a compound of theinvention and a second therapeutic agent to a subject does not precludethe separate administration of that same therapeutic agent, any othersecond therapeutic agent or any compound of this invention to saidsubject at another time during a course of treatment.

Effective amounts of these second therapeutic agents are well known tothose skilled in the art and guidance for dosing may be found in patentsand published patent applications referenced herein, as well as in Wellset al., eds., Pharmacotherapy Handbook, 2nd Edition, Appleton and Lange,Stamford, Conn. (2000); PDR Pharmacopoeia, Tarascon Pocket Pharmacopoeia2000, Deluxe Edition, Tarascon Publishing, Loma Linda, Calif. (2000),and other medical texts. However, it is well within the skilledartisan's purview to determine the second therapeutic agent's optimaleffective-amount range.

In one embodiment of the invention where a second therapeutic agent isadministered to a subject, the effective amount of the compound of thisinvention is less than its effective amount would be where the secondtherapeutic agent is not administered. In another embodiment, theeffective amount of the second therapeutic agent is less than itseffective amount would be where the compound of this invention is notadministered. In this way, undesired side effects associated with highdoses of either agent may be minimized. Other potential advantages(including without limitation improved dosing regimens and/or reduceddrug cost) will be apparent to those of skill in the art.

In yet another aspect, the invention provides the use of a compound offormula I alone or together with one or more of the above-describedsecond therapeutic agents in the manufacture of a medicament, either asa single composition or as separate dosage forms, for treatment orprevention in a subject of a disease, disorder or symptom set forthabove. Another aspect of the invention is a compound of the formulaeherein for use in the treatment or prevention in a subject of a disease,disorder or symptom thereof delineated herein.

Diagnostic Methods and Kits

The compounds and compositions of this invention are also useful asreagents in methods for determining the concentration of bosentan insolution or biological sample such as plasma, examining the metabolismof bosentan and other analytical studies.

According to one embodiment, the invention provides a method ofdetermining the concentration, in a solution or a biological sample, ofbosentan, comprising the steps of:

-   -   a) adding a known concentration of a compound of Formula I to        the solution of biological sample;    -   b) subjecting the solution or biological sample to a measuring        device that distinguishes bosentan from a compound of Formula I;    -   c) calibrating the measuring device to correlate the detected        quantity of the compound of Formula I with the known        concentration of the compound of Formula I added to the        biological sample or solution; and    -   d) measuring the quantity of bosentan in the biological sample        with said calibrated measuring device; and    -   e) determining the concentration of bosentan in the solution of        sample using the correlation between detected quantity and        concentration obtained for a compound of Formula I.

Measuring devices that can distinguish bosentan from the correspondingcompound of Formula I include any measuring device that can distinguishbetween two compounds that differ from one another only in isotopicabundance. Exemplary measuring devices include a mass spectrometer, NMRspectrometer, or IR spectrometer.

In another embodiment, the invention provides a method of evaluating themetabolic stability of a compound of Formula I comprising the steps ofcontacting the compound of Formula I with a metabolizing enzyme sourcefor a period of time and comparing the amount of the compound of FormulaI with the metabolic products of the compound of Formula I after theperiod of time.

In a related embodiment, the invention provides a method of evaluatingthe metabolic stability of a compound of Formula I in a patientfollowing administration of the compound of Formula I. This methodcomprises the steps of obtaining a serum, urine or feces sample from thepatient at a period of time following the administration of the compoundof Formula I to the subject; and comparing the amount of the compound ofFormula I with the metabolic products of the compound of Formula I inthe serum, urine or feces sample.

The present invention also provides kits for use to treat a condition ordisease selected from pulmonary arterial hypertension, scleroderma,chronic thromboembolic pulmonary hypertension, and idiopathic pulmonaryfibrosis. These kits comprise (a) a pharmaceutical compositioncomprising a compound of Formula I or a salt thereof; or a prodrug, or asalt of a prodrug thereof; or a hydrate, solvate, or polymorph thereof,wherein said pharmaceutical composition is in a container; and (b)instructions describing a method of using the pharmaceutical compositionto treat a condition or disease selected from pulmonary arterialhypertension, scleroderma, chronic thromboembolic pulmonaryhypertension, and idiopathic pulmonary fibrosis.

The container may be any vessel or other sealed or sealable apparatusthat can hold said pharmaceutical composition. Examples include bottles,divided or multi-chambered holders bottles, wherein each division orchamber comprises a single dose of said composition, a divided foilpacket wherein each division comprises a single dose of saidcomposition, or a dispenser that dispenses single doses of saidcomposition. The container can be in any conventional shape or form asknown in the art which is made of a pharmaceutically acceptablematerial, for example a paper or cardboard box, a glass or plasticbottle or jar, a re-sealable bag (for example, to hold a “refill” oftablets for placement into a different container), or a blister packwith individual doses for pressing out of the pack according to atherapeutic schedule. The container employed can depend on the exactdosage form involved, for example a conventional cardboard box would notgenerally be used to hold a liquid suspension. It is feasible that morethan one container can be used together in a single package to market asingle dosage form. For example, tablets may be contained in a bottle,which is in turn contained within a box. Preferably, the container is ablister pack.

The kits of this invention may also comprise a device to administer orto measure out a unit dose of the pharmaceutical composition. Suchdevice may include an inhaler if said composition is an inhalablecomposition; a syringe and needle if said composition is an injectablecomposition; a syringe, spoon, pump, or a vessel with or without volumemarkings if said composition is an oral liquid composition; or any othermeasuring or delivery device appropriate to the dosage formulation ofthe composition present in the kit.

In certain embodiment, the kits of this invention may comprise in aseparate vessel of container a pharmaceutical composition comprising asecond therapeutic agent, such as one of those listed above for use forco-administration with a compound of this invention.

SYNTHETIC EXAMPLES

The synthesis described below and illustrated in Scheme 5 provided keyintermediates for the preparation of compounds of this invention.

Example 1 Synthesis of4-d₉-tert-butyl-N-(6-chloro-5-(2-methoxyphenoxy)-2,2′-bipyrimidin-4-yl)benzenesulfonamide(Compound 17)

Step 1. Synthesis of d₉-tert-Butyl-benzene (Compound 20) A solution ofd₉-tert-butanol, 19 (25.0 g, 0.3012 mol, 1.0 equiv) in benzene (20 mL)was added over 0.25 hr to a suspension of iron(III) chloride (48.8 g,0.3012 mol, 1.0 equiv) in benzene (175 mL, 1.9615 mol, 6.5 equiv). Mildcooling was used to maintain the reaction temperature at 22-27° C.during the addition (benzene (5 mL) was used to rinse the additionfunnel). The suspension was stirred at room temperature for 7.5 hr thendiluted with hexanes (200 mL). The mixture was filtered through a pad ofsilica gel (0.5 in) topped with Celite (0.5 in), washing the pad withhexanes (700 mL). The filtrate was concentrated under reduced pressure(bath temperature about 20° C.) to give a yellow liquid. The crudeproduct was distilled to give 19.8 g (46%) of d₉-tert-butyl-benzene, 20as a colorless liquid, bp 55-60° C., 35-37 Torr).

Step 2. Synthesis of 4-d₉-tert-Butyl-benzene-1-sulfonyl chloride(Compound 21) A solution of d₉-tert-butyl-benzene, 20 (19.3 g, 0.135mol, 1.0 equiv) in chloroform (250 mL) was cooled to −5° C. in anice/brine bath. Chlorosulfonic acid (44.1 g, 25 mL, 0.377 mol, 2.8equiv) was added dropwise over 0.75 hr, maintaining the reactiontemperature at −5° C.±1° C. The ice/brine bath was replaced with anice/water bath and the mixture was stirred at 0-2° C. for 1 hr, thenallowed to warm to room temperature and stirred 1 hr. The turbid mixturewas poured cautiously onto ice (600 mL). The biphasic mixture wasdiluted with dichloromethane (200 mL). The organic phase was washed withwater (500 mL), brine (2×500 mL), dried (Na₂SO₄), filtered and thefiltrate concentrated under reduced pressure to give an oily solid. Theoily solid was placed under high vacuum for 1 hr to give 26.1 g (80%) ofcrude 4-d₉-tert-butyl-benzene-1-sulfonyl chloride, 21. The crude productwas used without further purification.

Step 3. Synthesis of 4-d₉-tert-Butyl-benzenesulfonamide (Compound 16) Amixture of about 15N ammonium hydroxide (24.6 mL, 0.3703 mol, 3.5 equiv)and tetrahydrofuran (200 mL) was cooled to about 2° C. and a solution ofcrude 4-d₉-tert-butyl-benzene-1-sulfonyl chloride, 21 (25.5 g, 0.1058mol, 1.0 equiv) in tetrahydrofuran (200 mL) was added dropwise over 0.75hr at 2-5° C. The mixture (some solids coating sides of flask) wasallowed to warm to room temperature and stirred 0.5 hr. Water (about 50mL) was added to dissolve solids and the mixture was concentrated underreduced pressure to remove the bulk of the tetrahydrofuran. The residualoily mixture was partitioned between ethyl acetate (500 mL) and 1Nhydrochloric acid (100 mL). The organic phase was washed with brine (100mL), dried (Na₂SO₄), filtered and the filtrate concentrated underreduced pressure to give a white solid, crude weight—25.9 g. TLC (30%ethyl acetate/heptanes)—product (R_(f)=0.47) and 3 minor impurities(R_(f)=0.73, R_(f)=0.66, R_(f)=0.54). The crude product was absorbedonto silica gel using dichloromethane and dry-loaded on a column ofsilica gel (250 g) packed in toluene. The column was eluted with toluene(1.5 L), 10% ethyl acetate/toluene (2 L) and 25% ethyl acetate/toluene(1 L). The one mixed fraction was purified a second time by silica gelchromatography (150 g), eluting with a gradient of 0-30% ethylacetate/heptanes. Product fractions from both columns were concentratedunder reduced pressure to give a white solid that was triturated withheptanes (150 mL), filtered and dried to give 21.9 g (93%) of4-d₉-tert-Butyl-benzenesulfonamide, 16. ¹H-NMR (300 MHz, CDCl₃): δ 4.93(s, 2H), 7.52 (d, J=8.2, 2H), 7.86 (d, J=8.7, 2H). HPLC (method: 20 mmC18-RP column-gradient method 2-95% ACN+0.1% formic acid in 3.3 min with1.7 min hold at 95% ACN; Wavelength: 254 nm): retention time=3.10 min.LCMS (M+H⁺): 223.2, 206.1.

Step 4. Synthesis of4-d₉-tert-Butyl-N-(6-chloro-5-(2-methoxyphenoxy)-2,2′-bipyrimidin-4-yl)benzenesulfonamide(Compound 17) 60% Sodium hydride (0.97 g, 24.2 mmol, 2.2 equiv) wassuspended in N,N′dimethylacetamide (50 mL) and the mixture was cooled inan ice-bath. 4-d₉-tert-Butyl-benzenesulfonamide, 16 (2.44 g, 11 mmol,1.1 equiv) was added portionwise as a solid, maintaining the reactiontemperature at >3° C. The white suspension was allowed to warm to roomtemperature over 0.75 hr, then cooled to ˜5° C.4,6-dichloro-5-(2-methoxyphenoxy)-2,2-bipyrimidine, 15 [prepared by themethod described in Bioorg. & Med. Chem. Letters, 2001, 9, 2955] (3.49g, 10 mmol, 1.0 equiv) was added as a solid. The reaction mixturedeveloped a yellow color but no exotherm was observed. The mixture wasstirred at 2-5° C. for 0.25 hr (slow H₂ evolution), then was allowed towarm to room temperature and was stirred 3.5 hr (the rate of H₂evolution increased as the mixture warmed, and the color of the mixturedeepened to yellow-orange). The suspension was poured slowly intoice-water (200 mL) and the yellow suspension was adjusted to pH 1-2 with1N hydrochloric acid. The yellow solid was filtered, washed with water(300 mL), dried on the filter for 1.5 hr, then dried overnight in avacuum oven at 40-50° C. The crude product was dissolved in a minimumamount of dichloromethane containing a few mL of methanol and wasabsorbed onto silica gel. The absorbed material was dry-loaded onto acolumn of silica gel (65 g) packed in dichloromethane. The column waseluted with a gradient of 0-5% methanol/dichloromethane (slow elution).Clean product fractions were concentrated under reduced pressure to givea yellow foamy solid. The foamy solid was triturated with ethyl acetate(about 50 mL) to give a suspension. The suspension was concentrated tonear dryness and diluted with 1:1 ethyl acetate/heptanes (150 mL). Thesolid was filtered, washed with 1:1 ethyl acetate/heptanes (25 mL) anddried to give 3.51 g (66%) of4-d₉-tert-butyl-N-(6-chloro-5-(2-methoxyphenoxy)-2,2′-bipyrimidin-4-yl)benzenesulfonamide,17 as a light-yellow solid. ¹H-NMR (300 MHz, DMSO-d₆): δ 3.78 (s, 3H),6.59 (bs, 1H), 6.81 (t, J=7.6, 1H), 7.02 (t, J=7.6, 1H), 7.09 (d, J=7.6,1H), 7.42 (bs, 2H), 7.66 (t, J=4.7, 1H), 8.02 (bs, 2H), 9.05 (d, J=4.1,2H). HPLC (method: 150 mm C18-RP column-gradient method 5-95% ACN;Wavelength: 254 nm): retention time=3.85 min. LCMS (M+H⁺): 535.1.

Evaluation of Metabolic Stability

Certain in vitro liver metabolism studies have been described previouslyin the following references, each of which is incorporated herein intheir entirety: Obach, R S, Drug Metab Disp, 1999, 27:1350; Houston, J Bet al., Drug Metab Rev, 1997, 29:891; Houston, J B, Biochem Pharmacol,1994, 47:1469; Iwatsubo, T et al., Pharmacol Ther, 1997, 73:147; andLave, T, et al., Pharm Res, 1997, 14:152.

Microsomal Assay: The metabolic stability of compounds of Formula I istested using pooled liver microsomal incubations. Full scan LC-MSanalysis is then performed to detect major metabolites. Samples of thetest compounds, exposed to pooled human liver microsomes, are analyzedusing HPLC-MS (or MS/MS) detection. For determining metabolic stability,multiple reaction monitoring (MRM) is used to measure the disappearanceof the test compounds. For metabolite detection, Q1 full scans are usedas survey scans to detect the major metabolites.

Experimental Procedures: Human liver microsomes are obtained from acommercial source (e.g., XenoTech, LLC (Lenexa, Kans.)). The incubationmixtures are prepared as follows:

Reaction Mixture Composition

Liver Microsomes 0.5-2.0 mg/mL NADPH 1 mM Potassium Phosphate, pH 7.4100 mM Magnesium Chloride 10 mM Test Compound 0.1-1 μM.

Incubation of Test Compounds with Liver Microsomes: The reactionmixture, minus cofactors, is prepared. An aliquot of the reactionmixture (without cofactors) is incubated in a shaking water bath at 37°C. for 3 minutes. Another aliquot of the reaction mixture is prepared asthe negative control. The test compound is added into both the reactionmixture and the negative control at a final concentration of 1 μM. Analiquot of the reaction mixture is prepared as a blank control, by theaddition of plain organic solvent (not the test compound). The reactionis initiated by the addition of cofactors (not into the negativecontrols), and then incubated in a shaking water bath at 37° C. Aliquots(200 μL) are withdrawn in triplicate at multiple time points (e.g., 0,15, 30, 60, and 120 minutes) and combined with 800 μL of ice-cold 50/50acetonitrile/dH₂O to terminate the reaction. The positive controls,testosterone and propranolol, as well as Compound 1, are each runsimultaneously with the test compounds in separate reactions.

All samples are analyzed using LC-MS (or MS/MS). An LC-MRM-MS/MS methodis used for metabolic stability. Also, Q1 full scan LC-MS methods areperformed on the blank matrix and the test compound incubation samples.The Q1 scans serve as survey scans to identify any sample unique peaksthat might represent the possible metabolites. The masses of thesepotential metabolites can be determined from the Q1 scans.

SUPERSOMES™ Assay. Various human cytochrome P450-specific SUPERSOMES™are purchased from Gentest (Woburn, Mass., USA). A 1.0 mL reactionmixture containing 25 pmole of SUPERSOMES™, 2.0 mM NADPH, 3.0 mM MgCl,and 1 μM of a test compound in 100 mM potassium phosphate buffer (pH7.4) was incubated at 37° C. in triplicate. Positive controls contain 1μM of bosentan instead of a test compound. Negative controls usedControl Insect Cell Cytosol (insect cell microsomes that lacked anyhuman metabolic enzyme) purchased from GenTest (Woburn, Mass., USA).Aliquots (50 μL) are removed from each sample and placed in wells of amulti-well plate at various time points (e.g., 0, 2, 5, 7, 12, 20, and30 minutes) and to each aliquot is added 50 μL of ice cold acetonitrilewith 3 μM haloperidol as an internal standard to stop the reaction.

Plates containing the removed aliquots are placed in −20° C. freezer for15 minutes to cool. After cooling, 100 μL of deionized water is added toall wells in the plate. Plates are then spun in the centrifuge for 10minutes at 3000 rpm. A portion of the supernatant (100 μL) is thenremoved, placed in a new plate and analyzed using Mass Spectrometry.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the illustrativeexamples, make and utilize the compounds of the present invention andpractice the claimed methods. It should be understood that the foregoingdiscussion and examples merely present a detailed description of certainpreferred embodiments. It will be apparent to those of ordinary skill inthe art that various modifications and equivalents can be made withoutdeparting from the spirit and scope of the invention.

1. A compound of the formula (I):

or a pharmaceutically acceptable salt thereof, wherein: each Y isindependently selected from hydrogen and deuterium, and Y^(2a) isadditionally selected from OH; each Z is independently selected fromhydrogen, deuterium, and fluorine; and at least one Y or Z is deuterium.2. (canceled)
 3. The compound of claim 1 wherein each Y¹ issimultaneously deuterium.
 4. The compound of claim 1 wherein each Y¹ issimultaneously hydrogen.
 5. The compound according to claim 1, whereinY^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h), and Y^(2i) arethe same.
 6. The compound of claim 5, wherein Y^(2a), Y^(2b), Y^(2c)Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h), and Y^(2i) are the same.
 7. Thecompound of claim 5, wherein Y^(2a) is OH.
 8. The compound of claim 5,wherein Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h), andY^(2i) are simultaneously deuterium.
 9. The compound of claim 5, whereinY^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h), and Y^(2i) aresimultaneously hydrogen.
 10. (canceled)
 11. The compound according toany one of claims 1 or 3 to 9, wherein Z^(1a) and Z^(1b) aresimultaneously deuterium.
 12. The compound according to any one ofclaims 1 or 3 to 9, wherein Z^(1a) and Z^(1b) are simultaneouslyhydrogen.
 13. The compound according to any one of claims 1 or 3 to 9,wherein Z^(1a) and Z^(1b) are simultaneously fluorine.
 14. The compoundof claim 1, wherein each Y¹ is the same; each of Y^(2b), Y^(2c) Y^(2d),Y^(2e), Y^(2f), Y^(2g), Y^(2h), Y^(2i) is the same; and each Z is thesame, the compound selected from any one of the compounds in the tablebelow or a salt thereof: Cmpd Each Y¹ Y^(2a) Y^(2b)-Y^(2i) Each Z 100 DH H D 101 D D D H 102 D H H H 103 H D D H 104 H H H D 105 H D D D 106 DD D D 107 D OH H D 108 D OH D H 109 D OH H H 110 H OH D H 111 H OH H D112 H OH D D 113 D OH D D 114 D H H F 115 D D D F 116 H D D F 117 D OH HF 118 D OH D F 119 H OH D F


15. The compound according to claim 1, wherein any atom not specified asdeuterium is present in its natural isotopic abundance.
 16. A compoundselected from:


17. A composition comprising a compound of the formula (I):

or a pharmaceutically acceptable salt thereof, wherein: each Y isindependently selected from hydrogen and deuterium and Y^(2a) isadditionally selected from OH; each Z is independently selected fromhydrogen, deuterium, and fluorine; at least one Y or Z is deuterium; andan acceptable carrier.
 18. The composition of claim 17, formulated forpharmaceutical administration, wherein the carrier is a pharmaceuticallyacceptable carrier.
 19. The composition of claim 18, further comprisinga second therapeutic agent useful in the treatment of a disease orcondition selected from pulmonary arterial hypertension, erectiledysfunction, chronic obstructive pulmonary disease, chronic pelvic painsyndrome type III, primary dysmenorrhea, pre-eclampsia, thalassemia,skin fibrosis, hypertension, hypoxia-induced pulmonary arteryhypertension, interstitial lung disease, scleroderma, idiopathicpulmonary fibrosis, pulmonary hypertension, chronic thromboembolicpulmonary hypertension, Eisenmenger's syndrome, benign prostatichyperplasia, high blood pressure, coronary disorders, cardiacinsufficiency, renal cerebral ischemia, cardiac infarct, migraine,subarachnoid haemorrhage, Raynaud syndrome, skin cancer,atherosclerosis, sickle cell disease, and digital ulcers.
 20. Thecomposition of claim 19, wherein said second therapeutic agent isselected from a prostacyclin, a prostacyclin derivative, a secondendothelin antagonist, a dopaminergic agonist, a phosphodiesteraseinhibitor, a sympathetic nervous system antagonist, an inhibitor ofendothelin converting enzyme, an antihypertensive, an alpha-adrenergicblocker, and an angiotensin II receptor antagonist.
 21. The compositionof claim 20, wherein said second therapeutic agent is selected from aphosphodiesterase V inhibitor, a prostacyclin, and a prostacyclinanalogue.
 22. The composition of claim 21, wherein saidphosphodiesterase V inhibitor is sildenafil.
 23. The composition ofclaim 21, wherein said second therapeutic agent is selected fromepoprostenol treprostinil, iloprost, and beraprost.
 24. A method oftreating a disease or condition selected from pulmonary arterialhypertension, erectile dysfunction, chronic obstructive pulmonarydisease, chronic pelvic pain syndrome type III, primary dysmenorrhea,pre-eclampsia, thalassemia, skin fibrosis, hypertension, hypoxia-inducedpulmonary artery hypertension, interstitial lung disease, scleroderma,idiopathic pulmonary fibrosis, pulmonary hypertension, chronicthromboembolic pulmonary hypertension, Eisenmenger's syndrome, benignprostatic hyperplasia, high blood pressure, coronary disorders, cardiacinsufficiency, renal cerebral ischemia, cardiac infarct, migraine,subarachnoid haemorrhage, Raynaud syndrome, skin cancer,atherosclerosis, sickle cell disease, and digital ulcers, in a patientin need thereof comprising the step of administering to said patient aneffective amount of a compound of the formula (I):

or a pharmaceutically acceptable salt thereof, wherein: each Y isindependently selected from hydrogen and deuterium, and Y^(2a) isadditionally selected from OH; each Z is independently selected fromhydrogen, deuterium, and fluorine; and at least one Y or Z is deuterium.25. The method of claim 24, wherein the disease or condition is selectedfrom pulmonary arterial hypertension, scleroderma and idiopathicpulmonary fibrosis.
 26. The method of claim 25, wherein the disease orcondition is pulmonary arterial hypertension.
 27. The method of claim24, comprising the additional step of co-administering to the patient asecond therapeutic agent selected from a prostacyclin, a prostacyclinderivative, a second endothelin antagonist, a dopaminergic agonist, aphosphodiesterase inhibitor, a sympathetic nervous system antagonist, aninhibitor of endothelin converting enzyme, an antihypertensive, analpha-adrenergic blocker, and an angiotensin II receptor antagonist. 28.The method of claim 27, wherein the second therapeutic agent is selectedfrom a phosphodiesterase V inhibitor, a prostacyclin, and a prostacyclinanalogue, and the disease or disorder is pulmonary arterialhypertension.
 29. The method of claim 28, wherein said secondtherapeutic agent is selected from epoprostenol treprostinil, iloprost,and beraprost.
 30. The method of claim 28, wherein said secondtherapeutic agent is sildenafil.
 31. A compound having the formula:


32. A compound selected from any one of:

each Y is independently selected from hydrogen or deuterium, and Y^(2a)is additionally selected from OH; each Z is independently selected fromhydrogen, deuterium, or fluorine; and at least one Y or Z is deuterium.33. The compound of claim 3, wherein Y^(2b), Y^(2c) Y^(2d), Y^(2e),Y^(2f), Y^(2g), Y^(2h), and Y^(2i) are the same.
 34. The compound ofclaim 3, wherein Y^(2b), Y^(2c) Y^(2d), Y^(2e), Y^(2f), Y^(2g), Y^(2h),and Y^(2i) are the same.